What causes a red scalp? A review of the most common causes

Scalp Redness: Top 13 Causes

Scalp redness has many causes. Here, I briefly review the top causes of scalp redness.

1) Seborrheic dermatitis.
Seborrheic dermatitis (SD) is an inflammatory condition of the scalp that affects about 3-5 % of adults. Males are more commonly affected than females. SD occurs on body sites where the skin is oily such as the scalp, eyebrows, sides of nose, eyelids and chest. Individuals with SD of the scalp develop red, flaky skin that is often itchy. The scales can be yellow, white or grey colored and are often described as being "greasy." This differs from scalp psoriasis where the scales are often silver and powdery (see below).

2) Psoriasis
Psoriasis is complex immune-based disease which can affect not only the skin, but also the nails and joints. Scalp psoriasis occurs in about 50 % of patients with skin psoriasis. Patients have scalp redness, flaking and scaling. Patients may also have bothersome itching. Although the redness and flaking often cause embarrassment, scalp psoriasis does not usually cause hair loss. 

3) Scarring alopecias
Scarring hair loss condition or "cicatricial alopecias” are a group of hair loss conditions which lead to permanent hair loss. These conditions may frequently be associated with redness of the scalp as well as scalp itching, burning and/or pain. These include conditions with names such as lichen planopilaris, folliculitis decalvans, lupus and several others.

4) Other inflammatory diseases
A wide variety of other inflammatory scalp conditions, including dermatomyositis and rosacea can be associated with scalp redness. A scalp biopsy can help differentiate these entities.
 

5) "Red Scalp Syndrome"
'Red scalp syndrome" is a condition which occurs in individuals who have persistent scalp redness that is not explainable by any other condition. The condition was first described  by Drs Thestrup and Hjorth Patients with the Red Scalp Syndrome may have itching and burning but typically do not have scaling or flaking.

6) Irritation

Many products that are applied to the scalp or hair can cause irritation. These include many cosmetic products, including gel, mousse, hair spray and hair dyes. Some treatments for hair loss can also be associated with irritation and redness, including minoxidil and other topical products containing irritants such propylene glycol.

7) Allergy
Shampoos, hair dyes and even some cosmetic products can cause allergic reactions in the scalp. Although some individuals with allergy have itching in the scalp, many do not. In such cases, a rash may be present on the neck, ears or back where the product came into contact with the skin.

8) Infection
Infections are a possible causes of redness. Bacterial, viral and fungal infections may cause redness in the scalp. Determining the specific cause may come from a careful history and scalp examination and sometimes submission of a swab or piece of scalp tissue to the microbiology laboratory. 

Bacteria, such as staphylococci, may cause infections of the scalp. Bacteria may also cause infection of the hair follicle, which is a condition called " bacterial folliculitis." A variety of viral infections cause scalp redness. Chicken pox and shingles are two such examples. Scalp ringworm or “tinea capitis” refers to infection of the scalp by certain types of fungi. Scalp redness and scaling may be seen in these cases.

9) Alopecia areata
Alopecia areata is an autoimmune condition affecting about 2 % of the population. IT is not typically a cause of scalp redness. The scalp in patients with alopecia areata is usually normal in color but may be pink or peach colored in some cases. 

10) Scalp Injury and Trauma
Patients with scalp injuries, either due to previous accidents or surgeries, may have persistent scalp redness. Burns from fire, chemicals or radiation can cause redness in the scalp. Burns from ultraviolet radiation, such as might occur on a sunny day, can cause scalp redness. Patients receiving radiation for head and neck cancers and brain tumors can also develop scalp redness. 

11) Sun damage
Patients with extensive sun damage, from years of sun expose, may frequently have a red scalp.

12) Cancers
A variety of pre cancers and cancers of the skin, including non melanoma skin cancers, can cause redness in localized areas of the scalp. A biopsy may be obtained to reach the diagnosis.

13) Polycythemia

Polycythemia is a rare condition that leads to an abnormal increase in red blood cell production. A 2003 study indicated the polycythemia is on the list of causes of a red scalp.


Conclusion
There are many causes of scalp redness. Fortunately, the cause of the redness can often be diagnosed from a thorough examination of the scalp. In complex or challenging situations, a scalp biopsy should be performed to confirm the diagnosis.